Retransmission of data to or from a mobile station, MS, or user equipment, UE, is previously known. It is also known to use a radio link control layer of a UMTS protocol structure in an acknowledged mode for dedicated channels.
In acknowledged mode, retransmissions are undertaken in case of detected transmission errors not recovered by forward error control. This is also called automatic repeat request, ARQ. With ARQ, retransmissions can be undertaken unless a transmitted message is (positively) acknowledged or if it is negatively acknowledged. Generally there are time limits for the respective positive and negative acknowledgements to be considered.
Within this patent application, a radio network controller, RNC, is understood as a network element including a radio resource controller. Node B is a logical node responsible for radio transmission/reception in one or more cells to/from User Equipment. A base station, BS, is a physical entity representing Node B.
Radio link control, RLC, is used within radio communications systems like General Packet Radio Services, GPRS, and UMTS.
International Patent Application WO0105121 describes a technique for providing a secure link in a mobile communication system including mechanisms for hard handover of a link in acknowledged mode. Data is tunneled.
A channel dedicated to a specific UE is referred to as a Dedicated Channel, DCH. A channel that is not a dedicated channel is called a common or shared channel.
UK patent application GB no. 0027148.6, describes channel switching between dedicated and common channels.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical Layer Procedures, 3G TS 25.301 v3.6.0, France, September 2000, specifies in chapter 5 Radio Interface Protocol Architecture of a UMTS system. There are three protocol layers:                physical layer, layer 1 or L1,        data link layer, layer 2 or L2, and        network layer, layer 3 or L3.        
Layer 2, L2, and layer 3, L3 are divided into Control and User Planes. Layer 2 consists of two sub-layers, RLC and MAC, for the Control Plane and 4 sub-layers, BMC, PDCP, RLC and MAC, for the User Plane. The acronyms BMC, PDCP, RLC and MAC denote Broadcast/Multicast Control, Packet Data Convergence Protocol, Radio Link Control and Medium Access Control respectively.
FIG. 1 illustrates a simplified UMTS layers 1 and 2 protocol structure for the so called Uu Stratum, UuS, or Radio Stratum, between a user equipment UE and a Universal Terrestrial Radio Access Network, UTRAN.
Radio Access Bearers, RABs, make available radio resources (and services) to user applications. For each mobile station there may be one or several RABs. Data flows (in the form of segments) from the RABs are passed to respective Radio Link Control, RLC, entities which amongst other tasks buffer the received data segments. There is one RLC entity for each RAB. In the RLC layer, RABs are mapped onto respective logical channels. A Medium Access Control, MAC, entity receives data transmitted in the logical channels and further maps logical channels onto a set of transport channels. One transport channel is Downlink Shared Channel, DSCH.
Transport channels are finally mapped to a single physical transport channel which has a total bandwidth allocated to it by the network. In frequency division duplex mode, a physical channel is defined by code, frequency and, in the uplink, relative phase (I/Q). In time division duplex mode a physical channel is defined by code, frequency, and time-slot. The DSCH, e.g., is mapped onto one or several physical channels such that a specified part of the downlink resources is employed.
PDCP provides mapping between Network PDUs (Protocol Data Units) of a network protocol, e.g. the Internet protocol, to an RLC entity. PDCP compresses and decompresses redundant Network PDU control information (header compression and decompression).
For transmissions on point-to-multipoint logical channels, BMC stores at UTRAN side Broadcast messages received from an RNC, calculates the required transmission rate and requests for the appropriate channel resources. It receives scheduling information from the RNC, and generates schedule messages. For transmission the messages are mapped on a point-to-multipoint logical channel. At the UE side, BMC evaluates the schedule messages and deliver Broadcast Messages to upper layer in the UE.
3G TS 25.301 also describes protocol termination, i.e. in which node of the UTRAN the radio interface protocols are terminated, or equivalently, where within UTRAN the respective protocol services are accessible. Section 5.6.5 describes protocol termination for DSCH. The RLC protocol for DSCH is terminated in Serving Radio Network Controller, SRNC, for both the control and user planes.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical Layer Procedures, 3G TS 25.322 v3.5.0, France, December 2000, specifies the RLC protocol. The RLC layer provides three services to the higher layers:                transparent data transfer service,        unacknowledged data transfer service, and        acknowledged data transfer Service        
Subsections 4.2.1.1 and 4.2.1.2 describe transparent mode entities and unacknowledged mode entities. Basically, RLC differences of the two modes reside in management of packet overhead. In transparent mode no overhead is added or removed by RLC. In subsection 4.2.1.3 an acknowledged mode entity, AM-entity, is described (see FIG. 4.4 of the 3GPP Technical Specification). In acknowledged mode automatic repeat request, ARQ, is used. The RLC sub-layer provides ARQ functionality closely coupled with the radio transmission technique used. The three modes                Transparent Mode, TM,        Unacknowledged Mode, UM, and        Acknowledged Mode, AMare hereinafter collectively referred to as RLC modes.        
None of the cited documents above discloses a dynamic RLC configuration and termination point.